- The neutrino is the oddest breed of fundamental particle. Neutrinos seem to defy all precedents set by better understood varieties of particles, such as electrons and quarks.
- Lightweight, shifty and exceedingly difficult to detect, neutrinos have been vexing experimentalists for decades.
- Even today fundamental properties of neutrinos remain up for debate. Some of the key questions pertain to the origin of their meager masses, the nature of neutrino antimatter and the number of neutrino species in existence, not to mention their penchant for switching identities on the fly.
- Uncovering the true nature of the neutrino may pave the way to a more unified theory of physics.
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Few physicists have had the privilege of bringing a new elementary particle into the world. When Wolfgang Pauli hit on the idea of the neutrino in 1930, however, internal misgivings tempered his response. “I have done a terrible thing,” Pauli later told his colleagues. “I have postulated a particle that cannot be detected.”
The neutrino is indeed elusive—its ghostly nature allows it to slip through almost all physical barriers, including the materials that physicists use in their particle detectors. In fact, most neutrinos pass cleanly through the earth without so much as brushing against another particle. Yet Pauli's fears turned out to be slightly overblown: the neutrino can be detected—although doing so requires great effort and experimental ingenuity.
This article was originally published with the title Ghostly Beacons of New Physics.